Transition to superdiffusive behavior in intracellular actin-based transport mediated by molecular motors

L. BRUNO, V. LEVI, M. BRUNSTEIN AND M. A. DESPÓSITO1

PHYSICAL REVIEW E - STATISTICAL PHYSICS, PLASMAS, FLUIDS AND RELATED INTERDISCIPLINARY TOPICS

American Physical Society

Año: 2009 vol. 80 p. 119121 - 119127

1063-651X

Intracellular transport of large cargoes, such as organelles, vesicles, or large proteins, is a complex dynami-cal process that involves the interplay of adenosine triphosphate–consuming molecular motors, cytoskeletonfilaments, and the viscoelastic cytoplasm. In this work we investigate the motion of pigment organelles
melanosomes driven by myosin-V motors in Xenopus laevis melanocytes using a high-spatio-temporal res-olution tracking technique. By analyzing the obtained trajectories, we show that the melanosomes mean-squaredisplacement undergoes a transition from a subdiffusive to a superdiffusive behavior. A stochastic theoreticalmodel, which explicitly considers the collective action of the molecular motors, is introduced to generalize theinterpretation of our data. Starting from a generalized Langevin equation, we derive an analytical expressionfor the mean square displacement, which also takes into account the experimental noise. By fitting theoreticalexpressions to experimental data we were able to discriminate the exponents that characterize the passive andactive contributions to the dynamics and to estimate the “global” motor forces correctly. Then, our model givesa quantitative description of active transport in living cells with a reduced number of parameters.